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HV supply User Guide
The GEM Supply Unit (GSU) consists of two dedicated power supply blocks: High Voltage Unit (HVU) and (optional) Low Voltage Unit (DCU). General Description HVU has 7 or 12 independently adjustable high voltage supplies while DCU contains 2 fixed supplies with high current capability. Outputs of HVU are connected together to form equivalent of voltage divider. It has special capabilities which makes it specially suited for GEM detectors. All voltages are generated as a sum of voltage sources instead of independent sources used in conventional solutions. This approach enables safe operation of detector as well as precise regulation of inter-electrode voltage instead of absolute electrode value. Moreover, after detection of HVU over-current event it can immediately and safely disconnect outputs, preventing GEM from being destroyed by an electric arc. Local Control mode The local mode is accessible using front panel keyboard and rotary knob with push button. All the time the front panel display shows (depending on the selected monitor mode): *DCU output voltages and currents (if available) *HVU output current *Voltages of channels (referenced to GND) *Voltage of channels (referenced to previous channel) *Matrix of the voltages all channels (from left to right and from up to down) Push the “Disp.mode/Esc” button to switch between available modes. All the settings can be done through the menu. Navigation over here is intuitive, Up/Down arrows (or scrolling using rotary knob) and Escape/Enter keys. To access this menu, press the "Menu/Enter" button in any of the monitor modes. The schema of menu (with short descrpition of functions and default values) is shown below: 1. HVU settings : 1.1 Output On/Off :: Enable/Disable channel :: - All (default: Off) :: - Ch. 1 (default: Off) :: - ... :: - Ch. 7(12) (default: Off) : 1.2 Voltage :: Set voltage for channel :: - All (default: 0V) :: - Ch. 1 (default: last value) :: - ... :: - Ch. 7(12) (default: last value) : 1.3 Slope :: On/Off and set slope value for channel :: - All (default: 10V/sec) :: - Ch. 1 (default: last value) :: - ... :: - Ch. 7(12) (default: last value) :: Notice: when the slope is off, then the valid slope value is equal 10V/sec : 1.4 Curr. limit :: Setting the current limit (default: 10µA) 2. DCU settings : 2.1 +/-5V settings :: Settings for DC outputs (both +5V and -5V): :: - On/Off (default: Off) :: - Current limit (default: 12A) : 2.2 +5V settings :: Settings for DC output (+5V): :: - On/Off (default: Off) :: - Current limit (default: 12A) : 2.3 -5V settings :: Settings for DC output (-5V): :: - On/Off (default: Off) :: - Current limit (default: 12A) 3. Runtime : Shows runtime for current session and total 4. Device ID : Shows unique device identification number The numeric data can be entered in two ways, as a value direct from the numeric keyboard or as an adjustment of the last value using rotary knob. In the second mode, the up/down arrow buttons allow to change the decade who can be incremented or decremented by the knob turnover. Currently selected decade is indicated by the marker just below. Press the "Menu/Enter" button to confirm and save the set value or "Disp.mode/Esc" button to discard change. Some of the settings are accessible through the shortcuts direct from the monitor modes. Press the knob in monitor mode (outside of the menu) to call setting: *On/Off the HVU channels *VHU channels voltage values *VHU channels slope values" *DCU on/off and overcurrent values Type of the called function depends on the current monitor mode. The voltage setting on the individual HVU channels is also accessible by pushing the corresponding numeric key in any of monitor modes. Select an appropiate decade using the Up/Down arrow buttons and turn the rotary knob to adjust the voltage value. Attention: In this adjustment mode, the change of the value causes immediatelly change of the output voltage the proper channel (according to the valid slope value). Diode indicators and key lock on the front panel Next to the each HV output is bi-color LED diode. The diode is turned off when corresponding channel is turned off. Green color of diode indicates that the channel is turned on. The diode illuminates red, when the channel is turned on and the diffrence between set and measured voltage value for this channel is greater than +/-20V. On the front panel is moreover key lock "HV Lock". If the HVU is locked, all channels are turned off regardless of the others settings. The "HV ON" diode indicates red. However if the HVU is unlocked the "HV ON" diode lights green and turning on of the channels is possible.